Method and device for terminal performing wlan measurement

ABSTRACT

Provided are a method for a terminal performing wireless local area network (WLAN) measurement in a wireless communication system, and a device supporting same. A terminal receives a WLAN measurement configuration comprising an indicator and a subject to be measured, and on the basis of the indicator, determines a subject for performing a WLAN measurement on, and performs a WLAN measurement on the determined subject for performing a WLAN measurement on, wherein the indicator may indicate whether a measurement of a WLAN AP detected by the terminal is allowed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2016/008453, filed on Aug. 1, 2016,which claims the benefit of U.S. Provisional Application No. 62/204,425filed on Aug. 12, 2015, the contents of which are all herebyincorporated by reference herein in their entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a wireless communication system, andmore particularly, to a method for performing, by a user equipment (UE),WLAN measurement in a wireless communication system, and a devicesupporting the same.

Related Art

3GPP (3rd Generation Partnership Project) LTE (Long Term Evolution) thatis an advancement of UMTS (Universal Mobile Telecommunication System) isbeing introduced with 3GPP release 8. In 3GPP LTE, OFDMA (orthogonalfrequency division multiple access) is used for downlink, and SC-FDMA(single carrier-frequency division multiple access) is used for uplink.The 3GPP LTE adopts MIMO (multiple input multiple output) having maximumfour antennas. Recently, a discussion of 3GPP LTE-A (LTE-Advanced) whichis the evolution of the 3GPP LTE is in progress.

A wireless communication system may support providing services to a userequipment (UE) through a plurality of access networks. A UE may receiveservices from a 3GPP access network, such as a mobile wirelesscommunication system, and may also receive services from a non-3GPPaccess network, such as a Worldwide Interoperability for MicrowaveAccess (WiMAX) network or a wireless local area network (WLAN).

A WLAN is a method based on a radio frequency technology, which enableswireless access to the Internet at home, at work, or in a particularservice-providing area using mobile devices, such as a personal digitalassistant (PDA), a laptop computer, and a portable multimedia player(PMP).

SUMMARY OF THE INVENTION

In WLAN measurement, measurement on detected WLAN APs other than WLANAPs listed by a WLAN measurement configuration and measurement resultreporting may be inappropriate. However, a network may need a report onthe measurement result of a WLAN AP detected by a UE other than the WLANAPs listed by the measurement configuration in order to achieve a SON.Therefore, the UE may need to report the measurement results of not onlythe WLAN APs listed by the WLAN measurement configuration but also theWLAN AP detected by the UE.

According to one embodiment, there is provided a method for performing,by a UE, wireless local area network (WLAN) measurement in a wirelesscommunication system. The method may include: receiving a WLANmeasurement configuration including an indicator and a measurementobject; determining an object of WLAN measurement based on theindicator; and performing WLAN measurement on the determined object ofWLAN measurement, wherein the indicator may indicate whether measurementon a WLAN AP detected by the UE is allowed.

When the indicator indicates that measurement on the detected WLAN AP isallowed, the object of WLAN measurement may include a listed WLAN AP andthe detected WLAN AP. When the measurement object includes WLANfrequency information, the detected WLAN AP may be a WLAN AP on a WLANfrequency listed in the WLAN frequency information. The listed WLAN APmay include at least one of a WLAN frequency list, a WLAN AP ID list,and a WLAN AP group ID list. The detected WLAN AP may not be included inthe listed WLAN AP but may be a WLAN AP detected by the UE.

When the indicator indicates that measurement on the detected WLAN AP isnot allowed, the object of WLAN measurement may include a listed WLANAP.

The method may further include reporting a WLAN measurement result.

The method may further include: determining an object of WLANmeasurement reporting based on the indicator; and reporting a WLANmeasurement result of the determined object of WLAN measurementreporting, wherein the indicator may indicate whether measurement resultreporting on the WLAN AP detected by the UE is allowed.

When the indicator indicates that measurement result reporting on thedetected WLAN AP is allowed, the object of WLAN measurement reportingmay include a listed WLAN AP and the detected WLAN AP. When themeasurement object includes WLAN frequency information, the detectedWLAN AP may be a WLAN AP on a WLAN frequency listed in the WLANfrequency information.

When the indicator indicates that measurement result reporting on thedetected WLAN AP is not allowed, the object of WLAN measurementreporting may be a listed WLAN AP

The WLAN measurement configuration may be received from a serving cell

The indicator may be included in the measurement object.

According to another embodiment, there is provided a UE for performingWLAN measurement in a wireless communication system. The UE may include:a memory; a transceiver; and a processor to connect the memory and thetransceiver, wherein the processor may be configured to: control thetransceiver to receive a WLAN measurement configuration comprising anindicator and a measurement object; determine an object of WLANmeasurement based on the indicator; and perform WLAN measurement on thedetermined object of WLAN measurement, wherein the indicator mayindicate whether measurement on a WLAN AP detected by the UE is allowed.

A UE may selectively perform measurement on a WLAN AP detected by the UEor measurement result reporting.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows LTE system architecture.

FIG. 2 shows a control plane of a radio interface protocol of an LTEsystem.

FIG. 3 shows a user plane of a radio interface protocol of an LTEsystem.

FIG. 4 shows a procedure in which UE that is initially powered onexperiences a cell selection process, registers it with a network, andthen performs cell reselection if necessary.

FIG. 5 shows an RRC connection establishment procedure.

FIG. 6 shows an RRC connection reconfiguration procedure.

FIG. 7 shows an RRC connection re-establishment procedure.

FIG. 8 shows a conventional method of performing measurement.

FIG. 9 shows the structure of a wireless local area network (WLAN)

FIG. 10 shows a method for a UE to perform WLAN measurement and WLANmeasurement reporting according to one embodiment of the presentinvention.

FIG. 11 shows a method for a UE to perform WLAN measurement according toone embodiment of the present invention.

FIG. 12 is a block diagram illustrating a wireless communication systemaccording to the embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The technology described below can be used in various wirelesscommunication systems such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), singlecarrier frequency division multiple access (SC-FDMA), etc. The CDMA canbe implemented with a radio technology such as universal terrestrialradio access (UTRA) or CDMA-2000. The TDMA can be implemented with aradio technology such as global system for mobile communications(GSM)/general packet ratio service (GPRS)/enhanced data rate for GSMevolution (EDGE). The OFDMA can be implemented with a radio technologysuch as institute of electrical and electronics engineers (IEEE) 802.11(Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved UTRA (E-UTRA), etc.IEEE 802.16m is evolved from IEEE 802.16e, and provides backwardcompatibility with a system based on the IEEE 802.16e. The UTRA is apart of a universal mobile telecommunication system (UMTS). 3rdgeneration partnership project (3GPP) long term evolution (LTE) is apart of an evolved UMTS (E-UMTS) using the E-UTRA. The 3GPP LTE uses theOFDMA in a downlink and uses the SC-FDMA in an uplink. LTE-advanced(LTE-A) is an evolution of the LTE.

For clarity, the following description will focus on LTE-A. However,technical features of the present invention are not limited thereto.

FIG. 1 shows LTE system architecture. The communication network iswidely deployed to provide a variety of communication services such asvoice over internet protocol (VoIP) through IMS and packet data.

Referring to FIG. 1, the LTE system architecture includes one or moreuser equipment (UE; 10), an evolved-UMTS terrestrial radio accessnetwork (E-UTRAN) and an evolved packet core (EPC). The UE 10 refers toa communication equipment carried by a user. The UE 10 may be fixed ormobile, and may be referred to as another terminology, such as a mobilestation (MS), a user terminal (UT), a subscriber station (SS), awireless device, etc.

The E-UTRAN includes one or more evolved node-B (eNB) 20, and aplurality of UEs may be located in one cell. The eNB 20 provides an endpoint of a control plane and a user plane to the UE 10. The eNB 20 isgenerally a fixed station that communicates with the UE 10 and may bereferred to as another terminology, such as a base station (BS), a basetransceiver system (BTS), an access point, etc. One eNB 20 may bedeployed per cell. There are one or more cells within the coverage ofthe eNB 20. A single cell is configured to have one of bandwidthsselected from 1.25, 2.5, 5, 10, and 20 MHz, etc., and provides downlinkor uplink transmission services to several UEs. In this case, differentcells can be configured to provide different bandwidths.

Hereinafter, a downlink (DL) denotes communication from the eNB 20 tothe UE 10, and an uplink (UL) denotes communication from the UE 10 tothe eNB 20. In the DL, a transmitter may be a part of the eNB 20, and areceiver may be a part of the UE 10. In the UL, the transmitter may be apart of the UE 10, and the receiver may be a part of the eNB 20.

The EPC includes a mobility management entity (MME) which is in chargeof control plane functions, and a system architecture evolution (SAE)gateway (S-GW) which is in charge of user plane functions. The MME/S-GW30 may be positioned at the end of the network and connected to anexternal network. The MME has UE access information or UE capabilityinformation, and such information may be primarily used in UE mobilitymanagement. The S-GW is a gateway of which an endpoint is an E-UTRAN.The MME/S-GW 30 provides an end point of a session and mobilitymanagement function for the UE 10. The EPC may further include a packetdata network (PDN) gateway (PDN-GW). The PDN-GW is a gateway of which anendpoint is a PDN.

The MME provides various functions including non-access stratum (NAS)signaling to eNBs 20, NAS signaling security, access stratum (AS)security control, Inter core network (CN) node signaling for mobilitybetween 3GPP access networks, idle mode UE reachability (includingcontrol and execution of paging retransmission), tracking area listmanagement (for UE in idle and active mode), P-GW and S-GW selection,MME selection for handovers with MME change, serving GPRS support node(SGSN) selection for handovers to 2G or 3G 3GPP access networks,roaming, authentication, bearer management functions including dedicatedbearer establishment, support for public warning system (PWS) (whichincludes earthquake and tsunami warning system (ETWS) and commercialmobile alert system (CMAS)) message transmission. The S-GW host providesassorted functions including per-user based packet filtering (by e.g.,deep packet inspection), lawful interception, UE Internet protocol (IP)address allocation, transport level packet marking in the DL, UL and DLservice level charging, gating and rate enforcement, DL rate enforcementbased on APN-AMBR. For clarity MME/S-GW 30 will be referred to hereinsimply as a “gateway,” but it is understood that this entity includesboth the MME and S-GW.

Interfaces for transmitting user traffic or control traffic may be used.The UE 10 and the eNB 20 are connected by means of a Uu interface. TheeNBs 20 are interconnected by means of an X2 interface. Neighboring eNBsmay have a meshed network structure that has the X2 interface. The eNBs20 are connected to the EPC by means of an S1 interface. The eNBs 20 areconnected to the MME by means of an S1-MME interface, and are connectedto the S-GW by means of S1-U interface. The S1 interface supports amany-to-many relation between the eNB 20 and the MME/S-GW.

The eNB 20 may perform functions of selection for gateway 30, routingtoward the gateway 30 during a radio resource control (RRC) activation,scheduling and transmitting of paging messages, scheduling andtransmitting of broadcast channel (BCH) information, dynamic allocationof resources to the UEs 10 in both UL and DL, configuration andprovisioning of eNB measurements, radio bearer control, radio admissioncontrol (RAC), and connection mobility control in LTE_ACTIVE state. Inthe EPC, and as noted above, gateway 30 may perform functions of pagingorigination, LTE_IDLE state management, ciphering of the user plane, SAEbearer control, and ciphering and integrity protection of NAS signaling.

FIG. 2 shows a control plane of a radio interface protocol of an LTEsystem. FIG. 3 shows a user plane of a radio interface protocol of anLTE system.

Layers of a radio interface protocol between the UE and the E-UTRAN maybe classified into a first layer (L1), a second layer (L2), and a thirdlayer (L3) based on the lower three layers of the open systeminterconnection (OSI) model that is well-known in the communicationsystem. The radio interface protocol between the UE and the E-UTRAN maybe horizontally divided into a physical layer, a data link layer, and anetwork layer, and may be vertically divided into a control plane(C-plane) which is a protocol stack for control signal transmission anda user plane (U-plane) which is a protocol stack for data informationtransmission. The layers of the radio interface protocol exist in pairsat the UE and the E-UTRAN, and are in charge of data transmission of theUu interface.

A physical (PHY) layer belongs to the L1. The PHY layer provides ahigher layer with an information transfer service through a physicalchannel. The PHY layer is connected to a medium access control (MAC)layer, which is a higher layer of the PHY layer, through a transportchannel. A physical channel is mapped to the transport channel Data istransferred between the MAC layer and the PHY layer through thetransport channel Between different PHY layers, i.e., a PHY layer of atransmitter and a PHY layer of a receiver, data is transferred throughthe physical channel using radio resources. The physical channel ismodulated using an orthogonal frequency division multiplexing (OFDM)scheme, and utilizes time and frequency as a radio resource.

The PHY layer uses several physical control channels. A physicaldownlink control channel (PDCCH) reports to a UE about resourceallocation of a paging channel (PCH) and a downlink shared channel(DL-SCH), and hybrid automatic repeat request (HARQ) information relatedto the DL-SCH. The PDCCH may carry a UL grant for reporting to the UEabout resource allocation of UL transmission. A physical control formatindicator channel (PCFICH) reports the number of OFDM symbols used forPDCCHs to the UE, and is transmitted in every subframe. A physicalhybrid ARQ indicator channel (PHICH) carries an HARQ acknowledgement(ACK)/non-acknowledgement (NACK) signal in response to UL transmission.A physical uplink control channel (PUCCH) carries UL control informationsuch as HARQ ACK/NACK for DL transmission, scheduling request, and CQI.A physical uplink shared channel (PUSCH) carries a UL-uplink sharedchannel (SCH).

A physical channel consists of a plurality of subframes in time domainand a plurality of subcarriers in frequency domain. One subframeconsists of a plurality of symbols in the time domain. One subframeconsists of a plurality of resource blocks (RBs). One RB consists of aplurality of symbols and a plurality of subcarriers. In addition, eachsubframe may use specific subcarriers of specific symbols of acorresponding subframe for a PDCCH. For example, a first symbol of thesubframe may be used for the PDCCH. The PDCCH carries dynamic allocatedresources, such as a physical resource block (PRB) and modulation andcoding scheme (MCS). A transmission time interval (TTI) which is a unittime for data transmission may be equal to a length of one subframe. Thelength of one subframe may be 1 ms.

The transport channel is classified into a common transport channel anda dedicated transport channel according to whether the channel is sharedor not. A DL transport channel for transmitting data from the network tothe UE includes a broadcast channel (BCH) for transmitting systeminformation, a paging channel (PCH) for transmitting a paging message, aDL-SCH for transmitting user traffic or control signals, etc. The DL-SCHsupports HARQ, dynamic link adaptation by varying the modulation, codingand transmit power, and both dynamic and semi-static resourceallocation. The DL-SCH also may enable broadcast in the entire cell andthe use of beamforming. The system information carries one or moresystem information blocks. All system information blocks may betransmitted with the same periodicity. Traffic or control signals of amultimedia broadcast/multicast service (MBMS) may be transmitted throughthe DL-SCH or a multicast channel (MCH).

A UL transport channel for transmitting data from the UE to the networkincludes a random access channel (RACH) for transmitting an initialcontrol message, a UL-SCH for transmitting user traffic or controlsignals, etc. The UL-SCH supports HARQ and dynamic link adaptation byvarying the transmit power and potentially modulation and coding. TheUL-SCH also may enable the use of beamforming. The RACH is normally usedfor initial access to a cell.

A MAC layer belongs to the L2. The MAC layer provides services to aradio link control (RLC) layer, which is a higher layer of the MAClayer, via a logical channel. The MAC layer provides a function ofmapping multiple logical channels to multiple transport channels. TheMAC layer also provides a function of logical channel multiplexing bymapping multiple logical channels to a single transport channel A MACsublayer provides data transfer services on logical channels.

The logical channels are classified into control channels fortransferring control plane information and traffic channels fortransferring user plane information, according to a type of transmittedinformation. That is, a set of logical channel types is defined fordifferent data transfer services offered by the MAC layer. The logicalchannels are located above the transport channel, and are mapped to thetransport channels.

The control channels are used for transfer of control plane informationonly. The control channels provided by the MAC layer include a broadcastcontrol channel (BCCH), a paging control channel (PCCH), a commoncontrol channel (CCCH), a multicast control channel (MCCH) and adedicated control channel (DCCH). The BCCH is a downlink channel forbroadcasting system control information. The PCCH is a downlink channelthat transfers paging information and is used when the network does notknow the location cell of a UE. The CCCH is used by UEs having no RRCconnection with the network. The MCCH is a point-to-multipoint downlinkchannel used for transmitting MBMS control information from the networkto a UE. The DCCH is a point-to-point bi-directional channel used by UEshaving an RRC connection that transmits dedicated control informationbetween a UE and the network.

Traffic channels are used for the transfer of user plane informationonly. The traffic channels provided by the MAC layer include a dedicatedtraffic channel (DTCH) and a multicast traffic channel (MTCH). The DTCHis a point-to-point channel, dedicated to one UE for the transfer ofuser information and can exist in both uplink and downlink. The MTCH isa point-to-multipoint downlink channel for transmitting traffic datafrom the network to the UE.

Uplink connections between logical channels and transport channelsinclude the DCCH that can be mapped to the UL-SCH, the DTCH that can bemapped to the UL-SCH and the CCCH that can be mapped to the UL-SCH.Downlink connections between logical channels and transport channelsinclude the BCCH that can be mapped to the BCH or DL-SCH, the PCCH thatcan be mapped to the PCH, the DCCH that can be mapped to the DL-SCH, andthe DTCH that can be mapped to the DL-SCH, the MCCH that can be mappedto the MCH, and the MTCH that can be mapped to the MCH.

An RLC layer belongs to the L2. The RLC layer provides a function ofadjusting a size of data, so as to be suitable for a lower layer totransmit the data, by concatenating and segmenting the data receivedfrom an upper layer in a radio section. In addition, to ensure a varietyof quality of service (QoS) required by a radio bearer (RB), the RLClayer provides three operation modes, i.e., a transparent mode (TM), anunacknowledged mode (UM), and an acknowledged mode (AM). The AM RLCprovides a retransmission function through an automatic repeat request(ARQ) for reliable data transmission. Meanwhile, a function of the RLClayer may be implemented with a functional block inside the MAC layer.In this case, the RLC layer may not exist.

A packet data convergence protocol (PDCP) layer belongs to the L2. ThePDCP layer provides a function of header compression function thatreduces unnecessary control information such that data being transmittedby employing IP packets, such as IPv4 or IPv6, can be efficientlytransmitted over a radio interface that has a relatively smallbandwidth. The header compression increases transmission efficiency inthe radio section by transmitting only necessary information in a headerof the data. In addition, the PDCP layer provides a function ofsecurity. The function of security includes ciphering which preventsinspection of third parties, and integrity protection which preventsdata manipulation of third parties.

A radio resource control (RRC) layer belongs to the L3. The RLC layer islocated at the lowest portion of the L3, and is only defined in thecontrol plane. The RRC layer takes a role of controlling a radioresource between the UE and the network. For this, the UE and thenetwork exchange an RRC message through the RRC layer. The RRC layercontrols logical channels, transport channels, and physical channels inrelation to the configuration, reconfiguration, and release of RBs. AnRB is a logical path provided by the L1 and L2 for data delivery betweenthe UE and the network. That is, the RB signifies a service provided theL2 for data transmission between the UE and E-UTRAN. The configurationof the RB implies a process for specifying a radio protocol layer andchannel properties to provide a particular service and for determiningrespective detailed parameters and operations. The RB is classified intotwo types, i.e., a signaling RB (SRB) and a data RB (DRB). The SRB isused as a path for transmitting an RRC message in the control plane. TheDRB is used as a path for transmitting user data in the user plane.

A Non-Access Stratum (NAS) layer placed over the RRC layer performsfunctions, such as session management and mobility management.

Referring to FIG. 2, the RLC and MAC layers (terminated in the eNB onthe network side) may perform functions such as scheduling, automaticrepeat request (ARQ), and hybrid automatic repeat request (HARQ). TheRRC layer (terminated in the eNB on the network side) may performfunctions such as broadcasting, paging, RRC connection management, RBcontrol, mobility functions, and UE measurement reporting andcontrolling. The NAS control protocol (terminated in the MME of gatewayon the network side) may perform functions such as a SAE bearermanagement, authentication, LTE_IDLE mobility handling, pagingorigination in LTE_IDLE, and security control for the signaling betweenthe gateway and UE.

Referring to FIG. 3, the RLC and MAC layers (terminated in the eNB onthe network side) may perform the same functions for the control plane.The PDCP layer (terminated in the eNB on the network side) may performthe user plane functions such as header compression, integrityprotection, and ciphering.

Hereinafter, An RRC state of a UE and RRC connection procedure aredescribed.

An RRC state indicates whether an RRC layer of the UE is logicallyconnected to an RRC layer of the E-UTRAN. The RRC state may be dividedinto two different states such as an RRC connected state and an RRC idlestate. When an RRC connection is established between the RRC layer ofthe UE and the RRC layer of the E-UTRAN, the UE is in RRC_CONNECTED, andotherwise the UE is in RRC_IDLE. Since the UE in RRC_CONNECTED has theRRC connection established with the E-UTRAN, the E-UTRAN may recognizethe existence of the UE in RRC_CONNECTED and may effectively control theUE. Meanwhile, the UE in RRC_IDLE may not be recognized by the E-UTRAN,and a CN manages the UE in unit of a TA which is a larger area than acell. That is, only the existence of the UE in RRC_IDLE is recognized inunit of a large area, and the UE must transition to RRC_CONNECTED toreceive a typical mobile communication service such as voice or datacommunication.

In RRC_IDLE state, the UE may receive broadcasts of system informationand paging information while the UE specifies a discontinuous reception(DRX) configured by NAS, and the UE has been allocated an identification(ID) which uniquely identifies the UE in a tracking area and may performpublic land mobile network (PLMN) selection and cell re-selection. Also,in RRC_IDLE state, no RRC context is stored in the eNB.

In RRC_CONNECTED state, the UE has an E-UTRAN RRC connection and acontext in the E-UTRAN, such that transmitting and/or receiving datato/from the eNB becomes possible. Also, the UE can report channelquality information and feedback information to the eNB. InRRC_CONNECTED state, the E-UTRAN knows the cell to which the UE belongs.Therefore, the network can transmit and/or receive data to/from UE, thenetwork can control mobility (handover and inter-radio accesstechnologies (RAT) cell change order to GSM EDGE radio access network(GERAN) with network assisted cell change (NACC)) of the UE, and thenetwork can perform cell measurements for a neighboring cell.

In RRC_IDLE state, the UE specifies the paging DRX cycle. Specifically,the UE monitors a paging signal at a specific paging occasion of everyUE specific paging DRX cycle. The paging occasion is a time intervalduring which a paging signal is transmitted. The UE has its own pagingoccasion.

A paging message is transmitted over all cells belonging to the sametracking area. If the UE moves from one TA to another TA, the UE willsend a tracking area update (TAU) message to the network to update itslocation.

When the user initially powers on the UE, the UE first searches for aproper cell and then remains in RRC_IDLE in the cell. When there is aneed to establish an RRC connection, the UE which remains in RRC_IDLEestablishes the RRC connection with the RRC of the E-UTRAN through anRRC connection procedure and then may transition to RRC_CONNECTED. TheUE which remains in RRC_IDLE may need to establish the RRC connectionwith the E-UTRAN when uplink data transmission is necessary due to auser's call attempt or the like or when there is a need to transmit aresponse message upon receiving a paging message from the E-UTRAN.

To manage mobility of the UE in the NAS layer, two states are defined,i.e., an EPS mobility management-REGISTERED (EMM-REGISTERED) state andan EMM-DEREGISTERED state. These two states apply to the UE and the MME.Initially, the UE is in the EMM-DEREGISTERED state. To access a network,the UE performs a process of registering to the network through aninitial attach procedure. If the attach procedure is successfullyperformed, the UE and the MME enter the EMM-REGISTERED state.

To manage a signaling connection between the UE and the EPC, two statesare defined, i.e., an EPS connection management (ECM)-IDLE state and anECM-CONNECTED state. These two states apply to the UE and the MME. Whenthe UE in the ECM-IDLE state establishes an RRC connection with theE-UTRAN, the UE enters the ECM-CONNECTED state. When the MME in theECM-IDLE state establishes an S1 connection with the E-UTRAN, the MMEenters the ECM-CONNECTED state. When the UE is in the ECM-IDLE state,the E-UTRAN does not have context information of the UE. Therefore, theUE in the ECM-IDLE state performs a UE-based mobility related proceduresuch as cell selection or reselection without having to receive acommand of the network. On the other hand, when the UE is in theECM-CONNECTED state, mobility of the UE is managed by the command of thenetwork. If a location of the UE in the ECM-IDLE state becomes differentfrom a location known to the network, the UE reports the location of theUE to the network through a tracking area update procedure.

FIG. 4 shows a procedure in which UE that is initially powered onexperiences a cell selection process, registers it with a network, andthen performs cell reselection if necessary.

Referring to FIG. 4, the UE selects Radio Access Technology (RAT) inwhich the UE communicates with a Public Land Mobile Network (PLMN), thatis, a network from which the UE is provided with service (S410).Information about the PLMN and the RAT may be selected by the user ofthe UE, and the information stored in a Universal Subscriber IdentityModule (USIM) may be used.

The UE selects a cell that has the greatest value and that belongs tocells having measured BS and signal intensity or quality greater than aspecific value (cell selection) (S420). In this case, the UE that ispowered off performs cell selection, which may be called initial cellselection. A cell selection procedure is described later in detail.After the cell selection, the UE receives system informationperiodically by the BS. The specific value refers to a value that isdefined in a system in order for the quality of a physical signal indata transmission/reception to be guaranteed. Accordingly, the specificvalue may differ depending on applied RAT.

If network registration is necessary, the UE performs a networkregistration procedure (S430). The UE registers its information (e.g.,an IMSI) with the network in order to receive service (e.g., paging)from the network. The UE does not register it with a network whenever itselects a cell, but registers it with a network when information aboutthe network (e.g., a Tracking Area Identity (TAI)) included in systeminformation is different from information about the network that isknown to the UE.

The UE performs cell reselection based on a service environment providedby the cell or the environment of the UE (S440). If the value of theintensity or quality of a signal measured based on a BS from which theUE is provided with service is lower than that measured based on a BS ofa neighboring cell, the UE selects a cell that belongs to other cellsand that provides better signal characteristics than the cell of the BSthat is accessed by the UE. This process is called cell reselectiondifferently from the initial cell selection of the No. 2 process. Inthis case, temporal restriction conditions are placed in order for acell to be frequently reselected in response to a change of signalcharacteristic. A cell reselection procedure is described later indetail.

FIG. 5 shows an RRC connection establishment procedure.

The UE sends an RRC connection request message that requests RRCconnection to a network (S510). The network sends an RRC connectionestablishment message as a response to the RRC connection request(S520). After receiving the RRC connection establishment message, the UEenters RRC connected mode.

The UE sends an RRC connection establishment complete message used tocheck the successful completion of the RRC connection to the network(S530).

FIG. 6 shows an RRC connection reconfiguration procedure.

An RRC connection reconfiguration is used to modify RRC connection. Thisis used to establish/modify/release RBs, perform handover, and setup/modify/release measurements.

A network sends an RRC connection reconfiguration message for modifyingRRC connection to UE (S610). As a response to the RRC connectionreconfiguration message, the UE sends an RRC connection reconfigurationcomplete message used to check the successful completion of the RRCconnection reconfiguration to the network (S620).

The following is a detailed description of a procedure of selecting acell by a terminal.

When power is turned-on or the terminal is located in a cell, theterminal performs procedures for receiving a service byselecting/reselecting a suitable quality cell.

A terminal in an RRC idle state should prepare to receive a servicethrough the cell by always selecting a suitable quality cell. Forexample, a terminal where power is turned-on just before should selectthe suitable quality cell to be registered in a network. If the terminalin an RRC connection state enters in an RRC idle state, the terminalshould selects a cell for stay in the RRC idle state. In this way, aprocedure of selecting a cell satisfying a certain condition by theterminal in order to be in a service idle state such as the RRC idlestate refers to cell selection. Since the cell selection is performed ina state that a cell in the RRC idle state is not currently determined,it is important to select the cell as rapid as possible. Accordingly, ifthe cell provides a wireless signal quality of a predetermined level orgreater, although the cell does not provide the best wireless signalquality, the cell may be selected during a cell selection procedure ofthe terminal.

Hereinafter, a method and a procedure of selecting a cell by a terminalin a 3GPP LTE is described.

A cell selection process is basically divided into two types.

The first is an initial cell selection process. In this process, UE doesnot have preliminary information about a wireless channel. Accordingly,the UE searches for all wireless channels in order to find out a propercell. The UE searches for the strongest cell in each channel Thereafter,if the UE has only to search for a suitable cell that satisfies a cellselection criterion, the UE selects the corresponding cell.

Next, the UE may select the cell using stored information or usinginformation broadcasted by the cell. Accordingly, cell selection may befast compared to an initial cell selection process. If the UE has onlyto search for a cell that satisfies the cell selection criterion, the UEselects the corresponding cell. If a suitable cell that satisfies thecell selection criterion is not retrieved though such a process, the UEperforms an initial cell selection process.

After the UE selects a specific cell through the cell selection process,the intensity or quality of a signal between the UE and a BS may bechanged due to a change in the mobility or wireless environment of theUE. Accordingly, if the quality of the selected cell is deteriorated,the UE may select another cell that provides better quality. If a cellis reselected as described above, the UE selects a cell that providesbetter signal quality than the currently selected cell. Such a processis called cell reselection. In general, a basic object of the cellreselection process is to select a cell that provides UE with the bestquality from a viewpoint of the quality of a radio signal.

In addition to the viewpoint of the quality of a radio signal, a networkmay determine priority corresponding to each frequency, and may informthe UE of the determined priorities. The UE that has received thepriorities preferentially takes into consideration the priorities in acell reselection process compared to a radio signal quality criterion.

As described above, there is a method of selecting or reselecting a cellaccording to the signal characteristics of a wireless environment. Inselecting a cell for reselection when a cell is reselected, thefollowing cell reselection methods may be present according to the RATand frequency characteristics of the cell.

-   -   Intra-frequency cell reselection: UE reselects a cell having the        same center frequency as that of RAT, such as a cell on which        the UE camps on.    -   Inter-frequency cell reselection: UE reselects a cell having a        different center frequency from that of RAT, such as a cell on        which the UE camps on    -   Inter-RAT cell reselection: UE reselects a cell that uses RAT        different from RAT on which the UE camps

The principle of a cell reselection process is as follows.

First, UE measures the quality of a serving cell and neighbor cells forcell reselection.

Second, cell reselection is performed based on a cell reselectioncriterion. The cell reselection criterion has the followingcharacteristics in relation to the measurements of a serving cell andneighbor cells.

Intra-frequency cell reselection is basically based on ranking. Rankingis a task for defining a criterion value for evaluating cell reselectionand numbering cells using criterion values according to the size of thecriterion values. A cell having the best criterion is commonly calledthe best-ranked cell. The cell criterion value is based on the value ofa corresponding cell measured by UE, and may be a value to which afrequency offset or cell offset has been applied, if necessary.

Inter-frequency cell reselection is based on frequency priority providedby a network. UE attempts to camp on a frequency having the highestfrequency priority. A network may provide frequency priority that willbe applied by UEs within a cell in common through broadcastingsignaling, or may provide frequency-specific priority to each UE throughUE-dedicated signaling. A cell reselection priority provided throughbroadcast signaling may refer to a common priority. A cell reselectionpriority for each terminal set by a network may refer to a dedicatedpriority. If receiving the dedicated priority, the terminal may receivea valid time associated with the dedicated priority together. Ifreceiving the dedicated priority, the terminal starts a validity timerset as the received valid time together therewith. While the valid timeris operated, the terminal applies the dedicated priority in the RRC idlemode. If the valid timer is expired, the terminal discards the dedicatedpriority and again applies the common priority.

For the inter-frequency cell reselection, a network may provide UE witha parameter (e.g., a frequency-specific offset) used in cell reselectionfor each frequency.

For the intra-frequency cell reselection or the inter-frequency cellreselection, a network may provide UE with a Neighboring Cell List (NCL)used in cell reselection. The NCL includes a cell-specific parameter(e.g., a cell-specific offset) used in cell reselection.

For the intra-frequency or inter-frequency cell reselection, a networkmay provide UE with a cell reselection black list used in cellreselection. The UE does not perform cell reselection on a cell includedin the black list.

Ranking performed in a cell reselection evaluation process is describedbelow.

A ranking criterion used to apply priority to a cell is defined as inEquation 1.

R _(S) =Q _(meas,s) +Q _(hyst) , R _(n) =Q _(meas,n) −Q_(offset)  [Equation 1]

In this case, Rs is the ranking criterion of a serving cell, Rn is theranking criterion of a neighbor cell, Qmeas,s is the quality value ofthe serving cell measured by UE, Qmeas,n is the quality value of theneighbor cell measured by UE, Qhyst is the hysteresis value for ranking,and Qoffset is an offset between the two cells.

In Intra-frequency, if UE receives an offset “Qoffsets,n” between aserving cell and a neighbor cell, Qoffset=Qoffsets,n. If UE does notQoffsets,n, Qoffset=0.

In Inter-frequency, if UE receives an offset “Qoffsets,n” for acorresponding cell, Qoffset=Qoffsets,n+Qfrequency. If UE does notreceive “Qoffsets,n”, Qoffset=Qfrequency.

If the ranking criterion Rs of a serving cell and the ranking criterionRn of a neighbor cell are changed in a similar state, ranking priorityis frequency changed as a result of the change, and UE may alternatelyreselect the twos. Qhyst is a parameter that gives hysteresis to cellreselection so that UE is prevented from to alternately reselecting twocells.

UE measures RS of a serving cell and Rn of a neighbor cell according tothe above equation, considers a cell having the greatest rankingcriterion value to be the best-ranked cell, and reselects the cell. If areselected cell is not a suitable cell, UE excludes a correspondingfrequency or a corresponding cell from the subject of cell reselection.

FIG. 7 shows an RRC connection re-establishment procedure.

Referring to FIG. 7, UE stops using all the radio bearers that have beenconfigured other than a Signaling Radio Bearer (SRB) #0, and initializesa variety of kinds of sublayers of an Access Stratum (AS) (S710).Furthermore, the UE configures each sublayer and the PHY layer as adefault configuration. In this procedure, the UE maintains the RRCconnection state.

The UE performs a cell selection procedure for performing an RRCconnection reconfiguration procedure (S720). The cell selectionprocedure of the RRC connection re-establishment procedure may beperformed in the same manner as the cell selection procedure that isperformed by the UE in the RRC idle state, although the UE maintains theRRC connection state.

After performing the cell selection procedure, the UE determines whetheror not a corresponding cell is a suitable cell by checking the systeminformation of the corresponding cell (S730). If the selected cell isdetermined to be a suitable E-UTRAN cell, the UE sends an RRC connectionre-establishment request message to the corresponding cell (S740).

Meanwhile, if the selected cell is determined to be a cell that uses RATdifferent from that of the E-UTRAN through the cell selection procedurefor performing the RRC connection re-establishment procedure, the UEstops the RRC connection re-establishment procedure and enters the RRCidle state (S750).

The UE may be implemented to finish checking whether the selected cellis a suitable cell through the cell selection procedure and thereception of the system information of the selected cell. To this end,the UE may drive a timer when the RRC connection re-establishmentprocedure is started. The timer may be stopped if it is determined thatthe UE has selected a suitable cell. If the timer expires, the UE mayconsider that the RRC connection re-establishment procedure has failed,and may enter the RRC idle state. Such a timer is hereinafter called anRLF timer. In LTE spec TS 36.331, a timer named “T311” may be used as anRLF timer. The UE may obtain the set value of the timer from the systeminformation of the serving cell.

If an RRC connection re-establishment request message is received fromthe UE and the request is accepted, a cell sends an RRC connectionre-establishment message to the UE.

The UE that has received the RRC connection re-establishment messagefrom the cell reconfigures a PDCP sublayer and an RLC sublayer with anSRB1. Furthermore, the UE calculates various key values related tosecurity setting, and reconfigures a PDCP sublayer responsible forsecurity as the newly calculated security key values. Accordingly, theSRB 1 between the UE and the cell is open, and the UE and the cell mayexchange RRC control messages. The UE completes the restart of the SRB1,and sends an RRC connection re-establishment complete message indicativeof that the RRC connection re-establishment procedure has been completedto the cell (S760).

In contrast, if the RRC connection re-establishment request message isreceived from the UE and the request is not accepted, the cell sends anRRC connection re-establishment reject message to the UE.

If the RRC connection re-establishment procedure is successfullyperformed, the cell and the UE perform an RRC connection reconfigurationprocedure. Accordingly, the UE recovers the state prior to the executionof the RRC connection re-establishment procedure, and the continuity ofservice is guaranteed to the upmost.

FIG. 8 shows a conventional method of performing measurement.

A UE receives measurement configuration information from a BS (S810). Amessage including the measurement configuration information is referredto as a measurement configuration message. The UE performs measurementbased on the measurement configuration information (S820). If ameasurement result satisfies a reporting condition included in themeasurement configuration information, the UE reports the measurementresult to the BS (S830). A message including the measurement result isreferred to as a measurement report message.

The measurement configuration information may include the followinginformation.

(1) Measurement object: The object is on which the UE performs themeasurements. The measurement object includes at least one of anintra-frequency measurement object which is an object of intra-frequencymeasurement, an inter-frequency measurement object which is an object ofinter-frequency measurement, and an inter-RAT measurement object whichis an object of inter-RAT measurement. For example, the intra-frequencymeasurement object may indicate a neighboring cell having the samefrequency as a frequency of a serving cell, the inter-frequencymeasurement object may indicate a neighboring cell having a differentfrequency from a frequency of the serving cell, and the inter-RATmeasurement object may indicate a neighboring cell of a different RATfrom an RAT of the serving cell.

(2) Reporting configuration: This includes a reporting criterion and areporting format. The reporting criterion is used to trigger the UE tosend a measurement report and can either be periodical or a single eventdescription. The reporting format is a quantity that the UE includes inmeasurement reporting and associated information (e.g. number of cellsto report).

(3) Measurement identify: Each measurement identity links onemeasurement object with one reporting configuration. By configuringmultiple measurement identities, it is possible to link more than onemeasurement object to the same reporting configuration, as well as tolink more than one reporting configuration to the same measurementobject. The measurement identity is used as a reference number inmeasurement reporting. The measurement identify may be included inmeasurement reporting to indicate a specific measurement object forwhich the measurement result is obtained and a specific reportingcondition according to which measurement reporting is triggered.

(4) Quantity configuration: One quantity configuration is configured perRAT type. The quantity configuration defines the measurement quantitiesand associated filtering used for all event evaluation and relatedreporting of that measurement type. One filter can be configured permeasurement quantity.

(5) Measurement gaps: Measurement gaps are periods that the UE may useto perform measurements when downlink transmission and uplinktransmission are not scheduled.

To perform a measurement procedure, the UE has a measurement object, areporting configuration, and a measurement identity.

In 3GPP LTE, the BS can assign only one measurement object to the UEwith respect to one frequency. Events for triggering measurementreporting are shown in the table 1. If the measurement result of the UEsatisfies the determined event, the UE transmits a measurement reportmessage to the BS.

TABLE 1 Event Reporting Condition Event A1 Serving becomes better thanthreshold Event A2 Serving becomes worse than threshold Event A3Neighbour becomes offset better than PCell/PSCell Event A4 Neighbourbecomes better than threshold Event A5 PCell/PSCell becomes worse thanthreshold1 and neighbour becomes better than threshold2 Event A6Neighbour becomes offset better than SCell Event B1 Inter RAT neighbourbecomes better than threshold Event B2 PCell becomes worse thanthreshold1 and inter RAT neighbour becomes better than threshold2 EventC1 CSI-RS resource becomes better than threshold Event C2 CSI-RSresource becomes offset better than reference CSI-RS resource

The measurement report may include the measurement identity, a measuredquality of the serving cell, and a measurement result of the neighborcell. The measurement identity identifies a measurement object in whichthe measurement report is triggered. The measurement result of theneighbor cell may include a cell identity and a measurement quality ofthe neighbor cell. The measured quality may include at least one ofreference signal received power (RSRP) and reference signal receivedquality (RSRQ).

FIG. 9 shows the structure of a wireless local area network (WLAN). FIG.9(a) illustrates the structure of an infrastructure network of Instituteof Electrical and Electronics Engineers (IEEE) 802.11. FIG. 9(b)illustrates an independent BSS.

Referring the FIG. 9(a), a WLAN system may include one or more basicservice sets (BSSs) 900 and 905. The BSSs 900 and 905 are a set of anaccess point (AP) and a station (STA), such as an AP 925 and STA1 900-1,which are successfully synchronized to communicate with each other, andare not a concept indicating a specific region. The BSS 905 may includeone AP 930 and one or more STAs 905-1 and 905-2 that may be connected tothe AP 930.

An infrastructure BSS may include at least one STA, APs 925 and 930providing a distribution service, and a distribution system (DS) 910connecting a plurality of APs.

The distribution system 910 may configure an extended service set (ESS)940 by connecting a plurality of BSSs 900 and 905. The ESS 940 may beused as a term indicating one network configured by connecting one ormore APs 925 or 930 through the distribution system 910. APs included inone ESS 940 may have the same service set identification (SSID).

A portal 920 may serve as a bridge that connects the WLAN (IEEE 802.11)and another network (for example, 802.X).

In the infrastructure network illustrated in the FIG. 9(a), a networkbetween the APs 925 and 930 and a network between the APs 925 and 930and the STAs 900-1, 905-1, and 905-2 may be configured. However, it ispossible to configure a network between STAs in the absence of the APs925 and 930 to perform communication. A network configured between STAsin the absence of the APs 925 and 930 to perform communication isdefined as an ad hoc network or independent basic service set (BSS).

Referring to FIG. 9(b), an independent BSS (IBSS) is a BSS that operatesin an ad hoc mode. The IBSS includes no AP and thus has no centralizedmanagement entity that performs a management function at the center.That is, in the IBSS, STAs 950-1, 950-2, 950-3, 955-4, and 955-5 aremanaged in a distributed manner. In the IBSS, all STAs 950-1, 950-2,950-3, 955-4, and 955-5 may be mobile STAs. Further, the STAs are notallowed to access the DS and thus establish a self-contained network.

An STA is a functional medium including medium access control (MAC) anda physical layer interface for a radio medium according to IEEE 802.11specifications and may be used to broadly mean both an AP and a non-APSTA.

An STA may also be referred to as various names, such as a mobileterminal, a wireless device, a wireless transmit/receive unit (WTRU),user equipment (UE), a mobile station (MS), a mobile subscriber unit, orsimply a user.

Hereinafter, WLAN measurement is described.

A UE supporting LTE-WLAN aggregation (LWA) may be set by an E-UTRAN toperform WLAN measurement. A WLAN measurement object may be set usingWLAN identifiers (BSSID, HESSID, and SSID), a WLAN channel number, and aWLAN band. A WLAN measurement report may be triggered using an RSSI. TheWLAN measurement report may include an RSSI, channel utilization, astation count, admission capacity, a backhaul rate, and a WLANidentifier. WLAN measurement may be configured to support at least oneof activation of LWA, inter WLAN mobility set mobility, or deactivationof LWA.

Hereinafter, measurement according to the cell type will be described.

A measurement procedure may be classified according to the cell type.Cells may be divided by type into a serving cell, a listed cell, and adetected cell. The serving cell may include a PCell and one or moreSCells when configured for a UE supporting carrier aggregation. Thelisted cell may be a cell listed as a measurement object. The detectedcell is not listed as a measurement object but may be a cell detected bya UE on a carrier frequency indicated by a measurement object.

In E-UTRA, a UE may measure and report a serving cell, a listed cell,and a detected cell. In WLAN measurement, however, it may be generallyinappropriate to report a detected AP on a particular WLAN channel. Thisis because there may be a plurality of APs not distributed by anoperator together with APs distributed by the operator on the samechannel, and thus the UE reporting detected APs may increase signalingoverheads. Further, this is because a BS may need only measurementresults of APs distributed by the operator for WLANaggregation/interworking enhancement. For the above reasons, in WLANmeasurement, it may be inappropriate to report a detected AP on aparticular WLAN channel. However, a network may wish to obtain themeasurement result of an AP not distributed by the operator in order toachieve an SON. That is, the network may wish to obtain the measurementresult of an AP that is not distributed by the operator but is detectedby the UE. Hereinafter, a method for a UE to perform WLAN measurementand to report a measured result and a device supporting the sameaccording to one embodiment of the present invention will be described.

FIG. 10 shows a method for a UE to perform WLAN measurement and WLANmeasurement reporting according to one embodiment of the presentinvention.

1. Step 1: UE receives WLAN measurement configuration (S1010)

(1) The UE may receive a WLAN measurement configuration from an LTEserving cell. The WLAN measurement configuration may include at leastone of a measurement object, a measurement metric, or a reportingconfiguration.

(2) The measurement object may include at least one of a WLAN frequencylist (that is, a WLAN channel list), a WLAN AP ID list, and a WLAN APgroup ID list.

The measurement object may include an indicator. The indicator mayindicate whether measurement on a WLAN AP detected by the UE is allowed.Alternatively, the indicator may indicate whether measurement resultreporting on the WLAN AP detected by the UE is allowed. Alternatively,the indicator may indicate whether measurement and measurement resultreporting on the WLAN AP detected by the UE is allowed. The detectedWLAN AP may be an unlisted WLAN AP. A BS may use the indicator toindicate whether measurement and/or measurement result reporting on thedetected WLAN AP is allowed.

(2) The measurement metric may be at least one of WLAN beacon RSSI,channel utilization in BSS load, an uplink (UL) backhaul rate, adownlink (DL) backhaul rate, a station (STA) count, and availableadmission.

(3) The reporting configuration may be a reporting criterion.

2. Step 2: UE performs WLAN measurement according to networkconfiguration (S1020)

(1) When measurement on the detected WLAN AP is not allowed for the UE,the UE may perform the WLAN measurement only on a listed WLAN APs and/ora listed WLAN AP group. That is, when the indicator indicates thatmeasurement on the detected WLAN AP is not allowed, the UE may performWLAN measurement only on the listed WLAN AP and/or the listed WLAN APgroup. The listed WLAN AP and/or the listed WLAN AP group may be a WLANAP distributed by an operator and/or a WLAN AP group distributed by theoperator.

For example, suppose that a first WLAN AP and a second WLAN AP are WLANAPs set to be measured, and a third WLAN AP and a fourth WLAN AP areWLAN APs detectable by the UE. When measurement on a detected WLAN AP isnot allowed for the UE, the UE may perform WLAN measurement only on thefirst WLAN AP and the second WLAN AP.

(2) When measurement on the detected WLAN AP is allowed for the UE, theUE may perform WLAN measurement not only on the listed WLAN AP and/orthe listed WLAN AP group but also on an unlisted WLAN AP and/or WLAN APgroup. That is, when the indicator indicates that measurement on thedetected WLAN AP is allowed, the UE may perform WLAN measurement notonly on the listed WLAN AP and/or the listed WLAN AP group but also on aWLAN AP and/or WLAN AP group detected by the UE.

-   -   When WLAN frequency information is included in the measurement        object, the detected WLAN AP and/or the detected WLAN AP group        may be limited to a WLAN AP and/or a group of a WLAN AP on a        frequency listed in the WLAN frequency information.    -   When no WLAN frequency information is included in the        measurement object, the UE may perform WLAN measurement on        unlisted WLAN APs and/or unlisted WLAN AP groups on all WLAN        frequencies. That is, when no WLAN frequency information is        included in the measurement object, the UE may perform WLAN        measurement on detected WLAN APs and/or detected WLAN AP groups        on all the WLAN frequencies.

For example, suppose that a first WLAN AP and a second WLAN AP are WLANAPs set to be measured, and a third WLAN AP and a fourth WLAN AP areWLAN APs detectable by the UE. When measurement on a detected WLAN AP isallowed for the UE, the UE may perform WLAN measurement on the firstWLAN AP, the second WLAN AP, the third WLAN AP, and the fourth WLAN AP.When measurement on a detected WLAN AP is allowed for the UE, WLANfrequency information is included in the measurement object, the thirdWLAN AP corresponds to a frequency listed in the WLAN frequencyinformation, and the fourth WLAN AP does not correspond to a frequencylisted in the WLAN frequency information, the UE may perform WLANmeasurement on the first WLAN AP, the second WLAN AP, and the third WLANAP. That is, in this case, since the fourth WLAN AP is detected by theUE but is not a WLAN AP on a frequency listed in the WLAN frequencyinformation, the UE may not perform WLAN measurement on the fourth WLANAP.

3. Step 3: UE performs WLAN measurement reporting according to networkconfiguration (S1030)

(1) When measurement result reporting on the detected WLAN AP is notallowed for the UE, the UE may perform WLAN measurement result reportingonly on the listed WLAN AP and/or the listed WLAN AP group. That is,when the indicator indicates that measurement result reporting on thedetected WLAN AP is not allowed, the UE may perform WLAN measurementresult reporting only on the listed WLAN AP and/or the listed WLAN APgroup.

For example, suppose that a first WLAN AP and a second WLAN AP are WLANAPs set as an object of measurement reporting, and a third WLAN AP and afourth WLAN AP are WLAN APs detectable by the UE. When measurementresult reporting on a detected WLAN AP is not allowed for the UE, the UEmay perform WLAN measurement result reporting only on the first WLAN APand the second WLAN AP.

For example, suppose that a first WLAN AP and a second WLAN AP are WLANAPs set as an object of measurement reporting, and a third WLAN AP and afourth WLAN AP are WLAN APs detectable by the UE. When measurement on adetected WLAN AP is allowed for the UE and measurement reporting on thedetected WLAN AP is not allowed for the UE, the UE may perform WLANmeasurement on the first WLAN AP, the second WLAN AP, the third WLAN AP,and the fourth WLAN AP and may perform measurement result reporting onlyon the first WLAN AP and the second WLAN AP.

(2) When measurement result reporting on the detected WLAN AP is allowedfor the UE, the UE may perform WLAN measurement result reporting notonly on the listed WLAN AP and/or the listed WLAN AP group but also onan unlisted WLAN AP and/or WLAN AP group. That is, when the indicatorindicates that measurement result reporting on the detected WLAN AP isallowed, the UE may perform WLAN measurement result reporting not onlyon the listed WLAN AP and/or the listed WLAN AP group but also on a WLANAP and/or WLAN AP group detected by the UE.

-   -   When WLAN frequency information is included in the measurement        object, the detected WLAN AP and/or the detected WLAN AP group        may be limited to a WLAN AP and/or a group of a WLAN AP on a        frequency listed in the WLAN frequency information.    -   When no WLAN frequency information is included in the        measurement object, the UE may perform WLAN measurement result        reporting on unlisted WLAN APs and/or unlisted WLAN AP groups on        all WLAN frequencies. That is, when no WLAN frequency        information is included in the measurement object, the UE may        perform WLAN measurement result reporting on detected WLAN APs        and/or detected WLAN AP groups on all the WLAN frequencies.

For example, suppose that a first WLAN AP and a second WLAN AP are WLANAPs set to be measured, and a third WLAN AP and a fourth WLAN AP areWLAN APs detectable by the UE. When measurement result reporting on adetected WLAN AP is allowed for the UE, the UE may perform WLANmeasurement on the first WLAN AP, the second WLAN AP, the third WLAN AP,and the fourth WLAN AP and may report the measurement results. Whenmeasurement result reporting on a detected WLAN AP is allowed for theUE, WLAN frequency information is included in the measurement object,the third WLAN AP corresponds to a frequency listed in the WLANfrequency information, and the fourth WLAN AP does not correspond to afrequency listed in the WLAN frequency information, the UE may performWLAN measurement on the first WLAN AP, the second WLAN AP, and the thirdWLAN AP and may report the WLAN measurement results. That is, in thiscase, since the fourth WLAN AP is detected by the UE but is not a WLANAP on a frequency listed in the WLAN frequency information, the UE maynot perform WLAN measurement and WLAN measurement reporting on thefourth WLAN AP.

According to one embodiment of the present invention, when the indicatorindicates that measurement on a WLAN AP detected by the UE is allowed,the UE may perform measurement and measurement result reporting on thedetected WLAN AP. Alternatively, when the indicator indicates thatmeasurement result reporting on a WLAN AP detected by the UE is allowed,the UE may perform measurement and measurement result reporting on thedetected WLAN AP. Alternatively, when the indicator indicates thatmeasurement and measurement result reporting on a WLAN AP detected bythe UE is allowed, the UE may perform measurement and measurement resultreporting on the detected WLAN AP.

FIG. 11 shows a method for a UE to perform WLAN measurement according toone embodiment of the present invention.

Referring to FIG. 11, the UE may receive a WLAN measurementconfiguration including an indicator and a measurement object (S1110).

The indicator may indicate whether measurement on a WLAN AP detected bythe UE is allowed. The WLAN measurement configuration may be receivedfrom a serving cell. The indicator may be included in the measurementobject.

The UE may determine an object of WLAN measurement based on theindicator (S1120).

When the indicator indicates that measurement on the detected WLAN AP isallowed, the object of WLAN measurement may include a listed WLAN AP andthe detected WLAN AP. When the indicator indicates that measurement onthe detected WLAN AP is not allowed, the object of WLAN measurement mayinclude a listed WLAN AP. The listed WLAN AP may include at least one ofa WLAN frequency list, a WLAN AP ID list, and a WLAN AP group ID list.The detected WLAN AP may not be included in the listed WLAN AP but maybe a WLAN AP detected by the UE. When the measurement object includesWLAN frequency information, the detected WLAN AP may be a WLAN AP on aWLAN frequency listed in the WLAN frequency information.

The UE may perform WLAN measurement on the determined object of WLANmeasurement (S1130). The UE may report a WLAN measurement result.

The UE may determine an object of WLAN measurement reporting based onthe indicator and may report a WLAN measurement result of the determinedobject of WLAN measurement reporting. The indicator may indicate whethermeasurement result reporting on the WLAN AP detected by the UE isallowed.

When the indicator indicates that measurement result reporting on thedetected WLAN AP is allowed, the object of WLAN measurement reportingmay include a listed WLAN AP and the detected WLAN AP. When theindicator indicates that measurement result reporting on the detectedWLAN AP is not allowed, the object of WLAN measurement reporting may bea listed WLAN AP. When the measurement object includes WLAN frequencyinformation, the detected WLAN AP may be a WLAN AP on a WLAN frequencylisted in the WLAN frequency information.

FIG. 12 is a block diagram illustrating a wireless communication systemaccording to the embodiment of the present invention.

A BS 1200 includes a processor 1201, a memory 1202 and a transceiver1203. The memory 1202 is connected to the processor 1201, and storesvarious information for driving the processor 1201. The transceiver 1203is connected to the processor 1201, and transmits and/or receives radiosignals. The processor 1201 implements proposed functions, processesand/or methods. In the above embodiment, an operation of the basestation may be implemented by the processor 1201.

A UE 1210 includes a processor 1211, a memory 1212 and a transceiver1213. The memory 1212 is connected to the processor 1211, and storesvarious information for driving the processor 1211. The transceiver 1213is connected to the processor 1211, and transmits and/or receives radiosignals. The processor 1211 implements proposed functions, processesand/or methods. In the above embodiment, an operation of the UE may beimplemented by the processor 1211.

The processor may include an application-specific integrated circuit(ASIC), a separate chipset, a logic circuit, and/or a data processingunit. The memory may include a read-only memory (ROM), a random accessmemory (RAM), a flash memory, a memory card, a storage medium, and/orother equivalent storage devices. The transceiver may include abase-band circuit for processing a wireless signal. When the embodimentis implemented in software, the aforementioned methods can beimplemented with a module (i.e., process, function, etc.) for performingthe aforementioned functions. The module may be stored in the memory andmay be performed by the processor. The memory may be located inside oroutside the processor, and may be coupled to the processor by usingvarious well-known means.

Various methods based on the present specification have been describedby referring to drawings and reference numerals given in the drawings onthe basis of the aforementioned examples. Although each method describesmultiple steps or blocks in a specific order for convenience ofexplanation, the invention disclosed in the claims is not limited to theorder of the steps or blocks, and each step or block can be implementedin a different order, or can be performed simultaneously with othersteps or blocks. In addition, those ordinarily skilled in the art canknow that the invention is not limited to each of the steps or blocks,and at least one different step can be added or deleted withoutdeparting from the scope and spirit of the invention.

The aforementioned embodiment includes various examples. It should benoted that those ordinarily skilled in the art know that all possiblecombinations of examples cannot be explained, and also know that variouscombinations can be derived from the technique of the presentspecification. Therefore, the protection scope of the invention shouldbe determined by combining various examples described in the detailedexplanation, without departing from the scope of the following claims.

1-15. (canceled)
 16. A method for performing measurement in a wirelesscommunication system, the method performed by a user equipment (UE) andcomprising: performing the measurement; transmitting a measurementreport, based on a measurement configuration, wherein the measurementconfiguration includes first information including a wireless local areanetwork (WLAN) access point (AP) identifier (ID) list, wherein themeasurement configuration includes second information related to themeasurement report, wherein the measurement report includes anidentifier of a first WLAN AP which is detected by the UE and is notlisted in the WLAN AP ID list, based on second information representingthat the first WLAN AP is allowed to be included in the measurementreport; and wherein the measurement report includes an identifier of asecond WLAN AP which is listed in the WLAN AP ID list, based on theconfiguration information representing that the measurement report ofthe first WLAN AP is not allowed to be included in the measurementreport.
 17. The method of claim 16, wherein based on the secondinformation representing that the first WLAN AP which is detected by theUE and is not listed in the WLAN AP ID list is allowed to be included inthe measurement report, the measurement report includes both theidentifier of the first WLAN AP and the identifier of the second WLAN APwhich is listed in the WLAN AP ID list.
 18. The method of claim 16wherein the measurement configuration includes WLAN frequencyinformation.
 19. The method of claim 16, wherein the measurementconfiguration comprises at least one of a WLAN frequency list and a WLANAP group ID list.
 20. The method of claim 16, further comprising:determining, by the UE, at least one or more WLAN APs to be included inthe measurement report based on the second information.
 21. The methodof claim 16, wherein the measurement configuration is received from aserving cell.
 22. A user equipment (UE) for performing wireless localarea network (WLAN) measurement in a wireless communication system, theUE comprising: a memory; a transceiver; and a processor, operativelycoupled to the memory and the transceiver, wherein the processor isconfigured to: control the transceiver to perform the measurement, andcontrol the transceiver to transmit a measurement report, based on ameasurement configuration, wherein the measurement configurationincludes first information including a wireless local area network(WLAN) access point (AP) identifier (ID) list, wherein the measurementconfiguration includes second information related to the measurementreport, wherein the measurement report includes an identifier of a firstWLAN AP which is detected by the UE and is not listed in the WLAN AP IDlist, based on second information representing that the first WLAN AP isallowed to be included in the measurement report; and wherein themeasurement report includes an identifier of a second WLAN AP which islisted in the WLAN AP ID list, based on the configuration informationrepresenting that the measurement report of the first WLAN AP is notallowed to be included in the measurement report.
 23. The UE of claim22, wherein based on the second information representing that the firstWLAN AP which is detected by the UE and is not listed in the WLAN AP IDlist is allowed to be included in the measurement report, themeasurement report includes both the identifier of the first WLAN AP andthe identifier of the second WLAN AP which is listed in the WLAN AP IDlist.
 24. The UE of claim 22, wherein the measurement configurationincludes WLAN frequency information.
 25. The UE of claim 22, wherein themeasurement configuration comprises at least one of a WLAN frequencylist and a WLAN AP group ID list.
 26. The UE of claim 22, wherein theprocessor is configured to: determine at least one or more WLAN APs tobe included in the measurement report based on the second information.27. The UE of claim 22, wherein the measurement configuration isreceived from a serving cell.